Hypothermic circulatory arrest at 20 ℃ does not deteriorate coagulopathy compared to 28 ℃ in a pig model

It is believed that a lower temperature setting of hypothermic circulatory arrest (HCA) in thoracic aortic surgery causes coagulopathy, resulting in excessive bleeding. However, experimental studies that eliminate clinical factors are lacking. The objective of this study is to investigate the influence of the temperature setting of HCA on coagulation in a pig model. Ten pigs were divided into the following two groups: moderate temperature at 28 °C (group M, n = 5) or lower temperature at 20 °C (group L, n = 5). Two hours of HCA during a total of 4 h of cardiopulmonary bypass (CPB) were performed. Blood samples were obtained at the beginning (T1) and the end (T2) of the surgery, and coagulation capability was analyzed through standard laboratory tests (SLTs) and rotational thromboelastometry (ROTEM). In SLTs, hemoglobin, fibrinogen, platelet count, prothrombin time, and activated partial thromboplastin time were analyzed. In ROTEM analyses, clotting time and clot formation time of EXTEM, maximum clot firmness (MCF), and maximum clot elasticity (MCE) of EXTEM and FIBTEM were analyzed. Fibrinogen decreased significantly in both groups (group M, p = 0.008; group L, p = 0.0175) at T2, and FIBTEM MCF and MCE also decreased at T2. There were no differences regarding changes in parameters of SLTs and ROTEM between groups. CPB decreases coagulation capacity, contributed by fibrinogen. However, a lower temperature setting of HCA at 20 °C for 2 h did not significantly affect coagulopathy compared to that of HCA at 28 °C after re-warming to 37 °C.

Turbulence in surgical suction heads as detected by MRI

BACKGROUND

Blood loss is common during surgical procedures, especially in open cardiac surgery. Allogenic blood transfusion is associated with increased morbidity and mortality. Blood conservation programs in cardiac surgery recommend re-transfusion of shed blood directly or after processing, as this decreases transfusion rates of allogenic blood. But aspiration of blood from the wound area is often associated with increased hemolysis, due to flow induced forces, mainly through development of turbulence.

METHODS

We evaluated magnetic resonance imaging (MRI) as a qualitative tool for detection of turbulence. MRI is sensitive to flow; this study uses velocity-compensated T1-weighted 3D MRI for turbulence detection in four geometrically different cardiotomy suction heads under comparable flow conditions (0-1250 mL/min).

RESULTS

Our standard control suction head Model A showed pronounced signs of turbulence at all flow rates measured, while turbulence was only detectable in our modified Models 1-3 at higher flow rates (Models 1 and 3) or not at all (Model 2).

CONCLUSIONS

The comparison of flow performance of surgical suction heads with different geometries via acceleration-sensitized 3D MRI revealed significant differences in turbulence development between our standard control Model A and the modified alternatives (Models 1-3). As flow conditions during measurement have been comparable, the specific geometry of the respective suction heads must have been the main factor responsible. The underlying mechanisms and causative factors can only be speculated about, but as other investigations have shown, hemolytic activity is positively associated with degree of turbulence. The turbulence data measured in this study correlate with data from other investigations about hemolysis induced by surgical suction heads. The experimental MRI technique used showed added value for further elucidating the underlying physical phenomena causing blood damage due to non-physiological flow.

Neural network-based modeling of the number of microbubbles generated with four circulation factors in cardiopulmonary bypass

The need for the estimation of the number of microbubbles (MBs) in cardiopulmonary bypass surgery has been recognized among surgeons to avoid postoperative neurological complications. MBs that exceed the diameter of human capillaries may cause endothelial disruption as well as microvascular obstructions that block posterior capillary blood flow. In this paper, we analyzed the relationship between the number of microbubbles generated and four circulation factors, i.e., intraoperative suction flow rate, venous reservoir level, continuous blood viscosity and perfusion flow rate in cardiopulmonary bypass, and proposed a neural-networked model to estimate the number of microbubbles with the factors. Model parameters were determined in a machine-learning manner using experimental data with bovine blood as the perfusate. The estimation accuracy of the model, assessed by tenfold cross-validation, demonstrated that the number of MBs can be estimated with a determinant coefficient R² = 0.9328 (p < 0.001). A significant increase in the residual error was found when each of four factors was excluded from the contributory variables. The study demonstrated the importance of four circulation factors in the prediction of the number of MBs and its capacity to eliminate potential postsurgical complication risks.

Comparison of three infant venous reservoirs with vacuum-assisted venous drainage during varying levels of cardiotomy suction

BACKGROUND

Vacuum-assisted venous drainage has gained widespread use within the pediatric perfusion community for use during cardiopulmonary bypass. It is questioned whether its efficiency may be compromised with application of excessive cardiotomy suction to the infant hard-shell venous reservoir. An in vitro simulation circuit was used to research this phenomenon. A comparison of three different infant hard-shell venous reservoirs also took place to determine if one reservoir type was more advantageous when handling cardiotomy suction. The reservoirs tested were the Maquet VHK 11000, Medtronic Affinity Pixie, and Terumo Capiox FX05.

METHODS

The in vitro simulation circuit consisted of a 1 L reservoir bag that was cannulated at one access point with an Edwards Lifesciences 10Fr aortic cannula and the other access area with an Edwards Lifesciences 10Fr right angle venous cannula and 12Fr right angle venous cannula that were joined together. Key points of measurement and response variables were the pressures on the connection of the venous cannulas, inlet of the venous reservoir, and flow through the venous line. Vacuum was applied and manipulated with a Maquet VAVD Controller to settings of -20 mmHg, -30 mmHg, -40 mmHg, -50 mmHg, and -60 mmHg. Cardiotomy suction was added at settings of 1 LPM, 2 LPM, 3 LPM, and 4 LPM. Values from each response variable were monitored and recorded. These data were utilized to compare the reservoirs with a random coefficient model for each response variable.

CONCLUSIONS

There is an adverse effect of excessive cardiotomy suction on the efficacy of vacuum-assisted venous drainage in infant hard-shell venous reservoirs. There is no significant difference between the VHK 11000, Pixie, and FX05 regarding their ability to handle this occurrence. An important discovery was that the FX05 showed a greater transfer of vacuum to the venous cannulas and reservoir inlet.

The effect of a novel turbulence-controlled suction system in the prevention of hemolysis and platelet dysfunction in autologous surgery blood

Background:

Re-transfusion of autologous blood is an important aspect of intraoperative blood management. Hemolysis and platelet dysfunction due to turbulence in the blood suction system strongly impede later usage of suction blood for re-transfusion. The aim of this study was to analyze the effects of a novel surgical-blood suction system with an automatic control setup for minimization of turbulence in the blood flow.

Methods:

We compared the turbulence-controlled suction system (TCSS) with a conventional suction system and untreated control blood in vitro. Blood cell counts, hemolysis levels according to free hemoglobin (fHb) and platelet function were analyzed to determine the integrity of the suction blood.

Results:

In the conventional suction system, we found a strong increase of the fHb levels. In contrast, erythrocyte integrity was almost completely preserved when using the TCSS. We obtained similar results regarding platelet function. The expression of platelet glycoproteins, such as GP IIb/IIIa and P-selectin, native or after stimulation with ADP, were markedly impaired by the conventional system, but not by the TCSS. In addition, platelet aggregometry revealed significant platelet dysfunction in conventional suction blood, but less aggregation impairments were present in blood samples from the TCSS.

Conclusion:

Our findings on an in vitro assessment show major improvements in red blood cell integrity and platelet function of suction blood when using the TCSS compared to a conventional suction system. These results reflect a significant benefit for autologous re-transfusion. We suggest testing the TCSS in surgery for clinical evaluation.

Improving hemolysis levels associated with cardiotomy suction

BACKGROUND

The major source of hemolysis during cardiopulmonary bypass (CPB) remains the cardiotomy suction.¹ Previous research has shown that the combination of negative pressures and the massive air-blood interface exponentially increases hemolysis in suctioned blood.

OBJECTIVE

This research aims to decrease hemolysis by eliminating the air-to-blood interface by implementing the Venturi effect to create powerful suction. This research effort hypothesizes that the Venturi suction will result in less hemolysis, indicated by lower plasma free hemoglobin levels (PFH) compared to current vacuum suction.

METHOD

The research hypothesizes that a paradigm approach to cardiotomy suction that utilizes the Venturi effect with shorter tubing lengths and weighted sucker tips will further reduce hemolysis.

RESULTS

The vacuum-suctioned blood showed PFH levels significantly increased from baseline levels (p=0.0039). Neither the Venturi nor paradigm groups showed PFH levels significantly increased from baseline levels (p=0.0625 and p=0.125, respectively). There was a significant difference in PFH levels among the three conditions (p<0.0001). The vacuum condition showed significantly higher levels of PFH compared to both the Venturi and the paradigm conditions (p<0.001 for both). There was no significant difference in the PFH levels between the Venturi and the paradigm groups (p=1.00).

CONCLUSION

This study concludes that vacuum suction causes excessive hemolysis. A Venturi-powered suction system does not cause hemolysis and can be employed to reduce the damaging effects of vacuum suction on blood.

Overcoming Challenges in the Management of Critical Events During Cardiopulmonary Bypass

Critical events during cardiopulmonary bypass (CPB) can challenge the most experienced perfusionists, anesthesiologists, and surgeons and can potentially lead to devastating outcomes. Much of the challenge of troubleshooting these events requires a key understanding of these situations and a well-defined strategy for early recognition and treatment. Adverse situations may be anticipated prior to going on CPB. Atherosclerosis is pervasive, and a high plaque burden may have implications in surgical technique modification and planning of CPB. Hematologic abnormalities such as cold agglutinins, antithrombin III deficiency, and hemoglobin S have been discussed with emphasis on managing complications arising from their altered pathophysiology. Jehovah’s witness patients require appropriate techniques for cell salvage to minimize blood loss. During initiation of CPB, devastating situations leading to acute hypoperfusion and multiorgan failure may be encountered in patients undergoing surgery for aortic dissection. Massive air emboli during CPB, though rare, necessitate an urgent diagnosis to detect the source and prompt management to contain catastrophic outcomes. Gaseous microemboli remain ubiquitous and continue to be a major concern for neurocognitive impairment despite our best efforts to improve techniques and refine the CPB circuit. During maintenance of CPB, adverse events reflect inability to provide optimal perfusion and can be ascribed to CPB machine malfunction or physiological aberrations. We also discuss critical events that can occur during perfusion and the need to monitor for organ perfusion in altered physiologic states emanating from hemodilution, hypothermia, and acid–base alterations.

Interferon gamma receptor expression on granulocytes of cardiac surgical patients is modulated differently by the type of cardiopulmonary bypass used

AIMS

To follow the IFNγ receptor expression on monocytes and granulocytes of cardiac surgical patients with respect to the type of cardiopulmonary bypass (CPB).

METHODS

Expression of IFNγ receptor on monocytes and granulocytes of 26 cardiac surgical patients operated with the use of either "standard" or "miniaturised" CPB was determined by flow cytometry.

RESULTS

The significant increase in IFNγ receptor expression on monocytes on the 1(st) and on the 3(rd) postoperative days was revealed in both groups of patients (p<0.001) irrespective of the type of CPB used, being non-significantly different between groups. In contrast, the expression of IFNγ on granulocytes displayed significant differences in terms of the CPB used. Whereas, in "standard" CPB patients, granulocyte INFγ receptor expression reached its maximum immediately after surgery (p<0.01), in "miniivasive" CPB patients, the peak in INFγ receptor expression was postponed to the 1(st) postoperative day (p<0.05). Statistically significantly higher IFNγ receptor expression on granulocytes was found in "standard" CPB patients (p<0.05).

CONCLUSION

Compared to "miniaturised" CPB patients, the significantly higher IFNγ receptor expression on granulocytes was found in "standard" CPB patients (p<0.05) on the 1(st) postoperative day.